Solve for a 15-a+4a=-6

$15 - a + 4 a = - 6$

Add $- a$ and $4 a$ .

$15 + 3 a = - 6$

Move all terms not containing $a$ to the right side of the equation.

Subtract $15$ from both sides of the equation.

$3 a = - 6 - 15$

Subtract $15$ from $- 6$ .

$3 a = - 21$

Divide each term in $3 a = - 21$ by $3$ and simplify.

Divide each term in $3 a = - 21$ by $3$ .

$\frac{3 a}{3} = \frac{- 21}{3}$

Simplify the left side.

Cancel the common factor of $3$ .

Cancel the common factor.

$\frac{3 a}{3} = \frac{- 21}{3}$

Divide $a$ by $1$ .

$a = \frac{- 21}{3}$

Simplify the right side.

Divide $- 21$ by $3$ .

$a = - 7$